Existing technologies for the equipment and operation of electrical appliances in household or commercial buildings includes transmission of current through a current distribution system to the electrical appliances. In such a distribution system, traditional electrical socket consists of a pair of T holes or jacks, which are aligned with plug bush connections. Currently the pins of an electrical plug can be inserted into the jacks and reach the plug bush connections in the socket directly, achieving the electrical connection purpose. Because most of such sockets are used in dwelling buildings and are located near the ground, latent electric shocking danger exists for children and infants. For example, they may insert small objects into the jacks. Moreover, when electrical contact occurs with the wet mouth of a child, a passage of electricity from the live line through the body of the child to the ground will be formed, resulting in grounding failure and burning or electrical shocking. Besides the fingers and mouth, the children may also insert various conductive materials such as metal objects into the sockets. Many such objects are commonly used ones, such as clips, electroprobes, hairpins, matches, keys and coils. Believing such objects are safe, some parents do not restrict contact with them. For this reason, every dwelling building is required to install protective electrical sockets and grounding failure breakers in the current distribution system of the whole building.
As for the currently available circuit breaking device, e.g. the device described in U.S. Pat. No. 4,595,894, jointly owned, a tripping device is used to mechanically break the electrical connection among one or more input/output wires. Such a device can be reset after it trips when finding a grounding failure. However, the grounding failure current breaker only breaks the current after current is contacted. Therefore, unless there is a protective electrical socket, the person may still undergo the initial temporary electric shocking.
The other patents, such as U.S. Pat. Nos. 2,552,061 and 2,610,999 are characterized by a notched sliding plate on the upper cover. It must be removed manually to match the notched sliding plate being covered to allow plugging in or unplugging off the electrical socket notch. The sliding closing plate provides better protection while adding an extra material layer between the plug pins and the socket connections. This reduces the contact area between the plug pins and the connections, resulting in a latent temperature rise or a dangerous electric arc. The manually moveable plate has another shortcoming: children, through observation, may learn to expose the electrical socket.
U.S. Pat. No. 7,355,117 mentions a protective electrical socket with an automatic resetting sliding block in it. However, because of the structural restriction of the sliding block in such a protective electrical socket, the material consumption and the fabrication cost are high.